1. Field of the Invention
The invention relates to the field of fluidics and in particular to coupling devices used in microfluidic circuits.
2. Description of the Prior Art
Rapidly developing Micro Electro Mechanical Systems (MEMS) technology makes micro fluidic systems very attractive for many applications, such as micro heat exchangers, micro chromatographs, biochemical detectors, micro mass spectrometers, micro reactors, and micro fluid control systems (e.g., microchannels, micro valves, micro pumps, and micro flow meters). It is quite challenging to transfer fluids between a micro fluidic system and its macroscopic environment because of micron-scale dimensions. There is no effective and simple way to apply conventional fluidic couplers to microscale fluidic systems at this time. Currently, to achieve coupling, a tube with an inside diameter significantly larger than the size of the inlet or outlet is directly glued to the opening. The yield of this approach is usually very low due to tube misalignment and inlet or outlet blockage by excessive glue. In addition, the permissible number of couplings for a micro fluidic system is limited by the relatively large size of the tubing used, and may not be adequate for the system. Furthermore, such a coupling generally cannot withstand high pressures required in many applications.
In order to adapt to the rapidly growing demand for micro fluidic systems, a novel, low-cost, and highly reliable coupling technique is required. The micromachined fluidic couplers proposed and developed at the Caltech Micromachining Laboratory can fulfill this requirement.
The invention comprises a micromachined coupler for coupling a capillary having a first size to an orifice having a shape and a second size. The invention in particular comprises a substrate, and a cavity defined in the substrate defining the orifice. A body is provide which has a shape conforming the shape of the cavity. A through hole is defined through the body. The through hole has a size conforming to the first size of the capillary. The capillary is disposable into the through hole so that the capillary of the first size is coupled to the orifice of the second size without the first and second sizes necessarily being the same.
The cavity and the body have conforming slanting surfaces, and in particular the cavity and the body define truncated pyramidal shapes. The cavity and the body each have a truncated square pyramidal shape, a truncated triangular pyramidal shape, or a truncated conical shape.
The micromachined coupler may further comprise a tubing stopper defined in the through hole and/or a shoulder defined on a surface of the coupler for bonding to the substrate outside of the cavity.
Typically the size of the orifice is different than the size of the capillary.
The invention is also characterized as a method of fabricating a micromachined coupler for coupling a capillary having a first size to an orifice having a shape and a second size comprising the steps of masking a substrate from which will a body of the micromachined coupler will be formed. The masking forms a pattern to define a pyramidal structure in the substrate. The masked substrate is anisotropically etched to form the pyramidal structure including a pit in the pyramidal structure. A surface of substrate opposite the pyramidal structure is then provided with a patterned mask. A prismatic hole is defined through the substrate and communicated with the pit to provide a through hole through the substrate.
The step of anisotropically etching the masked substrate to form the pyramidal structure forms a simple truncated structure or a truncated structure with a basal shoulder.
In one embodiment the step of defining a prismatic hole through the substrate does not completely remove the pit so that a tubing stop is formed by a remaining portion of the pit. The method further comprises the step of disposing a capillary into the prismatic hole in a sealed relationship therewith.
The step of anisotropically etching the masked substrate to form the pyramidal structure forms a square, triangular or conical truncated structure.
The invention is still further defined as a method of fabricating a micromachined coupler for coupling a capillary having a first size to an orifice having a shape and a second size comprising the steps of defining a truncated pyramidal cavity in a micromachined mold. A material is disposed or deposited in the truncated pyramidal cavity to form a body of the coupler. A prismatic hole of a first size is defined through the body to define a through hole by deep reactive ion etching.
In another embodiment the method further comprises the step of defining by deep reactive ion etching a prismatic hole of a second size in the body aligned with the prismatic hole of the first size to define a tubing stop in the prismatic hole of the first size.
The invention now having been briefly summarized, turn to the following drawings wherein the invention may be better visualized and where like elements are reference by like numerals.